With the merits of being energy efficient and environmental friendly, LEDs are extensively used in various lighting applications including such as general lighting, backlights and signs. LED light bulbs intended to be used as replacement bulbs of traditional light sources including incandescent and fluorescent lamps are too becoming widely available. Typical LED light bulbs utilizing inorganic LED chips are, however, facing certain limitations to their design, development and implementation due to the limited angle of illumination and the high brightness point light nature as well as their sensitive performance and lifetime degradation with the increase of temperature.
It is known that the abovementioned drawbacks of LED light bulbs including at least the illumination angles as well as the cooling of LED shall be taken into consideration for the design and development of LED light bulbs. One solution to overcome the abovementioned drawbacks of LED light bulbs is described in Canadian Patent No. CA 2,687,529 (hereafter referred to as the '529 patent) entitled “LED Light Bulb with Improved Illumination and Heat Dissipation”, assigned to the present inventor. The '529 patent deals with both the illumination angle and the cooling issues associated with LED lamps and discloses an LED light bulb utilizing an LED light engine to provide up and down “direct lights” and a cooling structure to facilitate the heat dissipation from the LED light engine to the ambient. One potential shortcoming of the LED light bulb 10 disclosed by the '529 patent may be related to the lateral illumination or illumination projected to the sides of the bulb as shown in FIG. 1. The lateral illumination intended to cover the lateral sides of the light bulb 10 as depicted by the shaded area S in FIG. 1 may be limited due to the existing beam angle of individual LED and module currently available (approximately 120 degree for most LEDs). Another potential shortcoming may occur during the manufacturing and selection of various different types of LEDs including both top-view and side-view LEDs. Despite the fact that side-view LEDs may be utilized to cover the lateral illumination as shown in FIGS. 2˜6 of the '529 patent, such implementation involving variations of types of LEDs may, however, potentially complicate the manufacturing processes and introduce inconsistencies to the preparation and selection of LEDs of appropriate beam codes in accordance with for example 1931 CIE Chromaticity Diagram.
Organic LEDs (OLEDs), another main stream of solid state lighting in addition to inorganic LEDs, are known for their dispersed light nature and are being extensively developed as a solution for area lighting including general lighting for home and office environments. A prior OLED lighting device generally includes an organic light-emitting layer disposed between a cathode and an anode electrode, and the organic electroluminescent (EL) layer emits light upon the application of a voltage from a power source across the electrodes. The OLED device also includes a substrate comprising a material such as glass or plastic and is encapsulated with a cover; in addition, one of the two electrodes and either the cover or substrate may be made translucent to visible light spectrum to allow emitted light therethrough. Depending upon the transparency of the materials of the electrodes, the cover and/or the substrate used or selected, the OLED lighting device may be a top-emitting, a bottom-emitting or both. For example, U.S. Pat. No. 6,469,437 entitled “Highly Transparent Organic Light Emitting Device Employing a Non-metallic Cathode” by Parthasarathy et al., U.S. Pat. No. 6,515,417 entitled “Organic Light Emitting Device and Method for Mounting” by Duggal et al., U.S. Pat. No. 6,565,231 entitled “OLED Area Illumination Lighting Apparatus” by Cok, U.S. Pat. No. 6,994,906 entitled “Flexible Substrates for Organic Devices” by Burroughes et al., U.S. Pat. No. 7,288,330 entitled “High Performance White Light-emitting OLED Device” by Hatwar et all, U.S. Pat. No. 7,662,485 entitled “White Organic Light-emitting Devices with Improved Performance” disclose examples of OLED lighting elements for large area lighting.
Efforts in the manufacturing process and method of light sheets have too made organic or inorganic LED light sheets possible and available. OLED may be manufactured in a planar form in a relatively lower cost manner comparing to inorganic LEDs. Known processes of OLED include for example, U.S. Pat. No. 7,033,850 entitled “Roll-to-sheet Manufacture of OLED Materials” by Tyan et al., U.S. Pat. No. 7,166,006 entitled “Method of Manufacturing OLED Devices by Deposition on Curved Substrates” by Cok, and U.S. Pat. No. 7,259,030 entitled “Roll-to-roll Fabricated Light Sheet and Encapsulated Semiconductor Circuit Devices” by Daniels et al. disclose examples of the fabrication of OLED light sheets. Furthermore, inorganic LED light sheet with the replacement of the abovementioned EL material of OLEDs with an inorganic material is also possible; for instance, U.S. Pat. No. 6,111,274 entitled “Inorganic Light Emitting Diode” by Arai discloses an example of the LED light sheet.
One may evidently realize the benefits of the utilization of large area lighting devices or systems in the field of general lighting; however, there are still limitations to the implementation of such large area lighting sources. One of the problems associated with such implementation of area lighting is clearly the amount of efforts and costs necessary for the replacement of existing systems and lighting fixtures in great scale. Another problem is also related to the limited illumination angles of light sheets since organic or inorganic LED light sheets in a planar form may still be of a limited illumination angle of 120˜140 degrees in general and with limited “direct lights” to the lateral sides, as shown in FIG. 2A. Furthermore, the cooling of LEDs still needs to be considered, especially for high power LEDs utilizing greater currents. For solid state lighting utilizing semiconductor materials, effective cooling of LEDs is necessary since both organic and inorganic LEDs are sensitive to the increase of operating temperature; as larger current input may advantageously lead to a greater light output from the LED, but may too result in undesirable increases of the operating temperature of the LED, causing degradation of LED performance and lifetime.
In view of the above, the inventor intends to overcome the shortcomings of prior arts with the realization of the abovementioned possible drawbacks associated with large area lighting in general lighting for home and office environments. The main challenge of the present invention may be three-fold: one is to provide a light source or lighting device capable of generating direct lights in multiple directions and preferably including lateral sides of the light source such that a substantially spherical illumination of dispersed lights may be obtained (the term substantially “spherical illumination” recited herein may refer to luminous-intensity distribution curve measured by for example a Goniophotometer); another is to provide an LED light bulb utilizing an LED light engine having or adapting a minimal number and/or variation of LED modules such that the aforementioned possible discrepancies or inconsistencies among LEDs may be minimized and such that preparation and manufacturing of the LED light engine may be facilitated; and the other is to provide an effective cooling to the lighting apparatus utilizing solid state lighting of semiconductor materials and preferably involving less moving parts to prevent or reduce the likelihood of component failures. Furthermore, it is desirable to provide a lighting apparatus adapting to currently existing fixtures with ease such that efforts and costs in the replacement and modification of existing systems and lighting fixtures may be reduced. The LED light bulb and components thereof provided may too be of a durable, reliable and recyclable unit. In general, the inventor intends to advantageously provide a light source for home and office environments, which may too be an alternative solution to the one provided by the abovementioned large area lightings but without extensive hardware or lighting fixture replacements or modifications; in a narrower sense, it is desirable to provide a light source such that the abovementioned shortcomings including the limited beam angles, heat dissipation and inconsistent outputs among variations of LED units of the prior arts may be overcome.